The present invention relates to addition, pigment or colorant materials which may be used for laser marking, and more particularly relates to bismuth-containing laser markable compositions, and methods of making and using such compositions.
The use of titanium dioxide as a laser markable pigment is disclosed in U.S. Pat. No. 5,091,284. However, laser marks produced from titanium dioxide suffer from poor contrast and durability. Although many different types of pigments are known, a need exists for a pigment which can be added to a substrate to produce high contrast durable laser marks.
This invention relates to the use of bismuth-containing compounds as an additive, pigment or colorant. The bismuth containing compounds are useful in substrates comprising organic chemical compositions such as plastics, rubbers and the like, and coating compositions such as paints, printing inks and the like. The bismuth-containing compounds are also useful in inorganic chemical composition substrates such as glass enamels, porcelain enamels and the like. The present bismuth-containing compounds may be used in such compositions to impart unique properties such as the ability to make high contrast laser marks and/or color changing interactions with laser beams, unique electronic properties and high IR reflectance.
An aspect of the present invention is to provide a pigment of the formula BixMyOz, where M is at least one metal selected from Zn, Ti, Fe, Cu, Al, Zr, P, Sn, Sr, Si, Y, Nb, La, Ta, Pr, Ca, Mg, Mo, W, Sb, Cr, Ba and Ce, x is from about 0.3 to about 70, y is from about 0.05 to about 8, and z is from about 1 to about 100.
A further aspect of the present invention is to provide a laser markable compound comprising an oxide of bismuth and at least one additional metal selected from Zn, Ti, Fe, Cu, Al, Zr, P, Sn, Sr, Si, Y, Nb, La, Ta, Pr, Ca, Mg, Mo, W, Sb, Cr, and Ce.
Another aspect of the present invention is to provide a laser markable substrate comprising a substrate material and a bismuth-containing compound dispersed in the substrate material.
A further aspect of the present invention is to provide laser marked substrate comprising a substrate material, a bismuth-containing compound dispersed in the substrate material, and a laser-marked portion of the bismuth-containing compound providing a contrasting mark on the substrate material.
Another aspect of the present invention is to provide a method of making a laser markable compound comprising the steps of mixing bismuth oxide or precursors thereof with at least one additional metal oxide or precursors thereof, and heating the mixture.
A further aspect of the present invention is to provide a method of making a laser markable substrate comprising dispersing a bismuth-containing compound in a substrate material.
Another aspect of the present invention is to provide a method of laser marking an article comprising providing a substrate including a bismuth-containing compound and irradiating at least a portion of the substrate with a laser to form a marking thereon.
These and other aspects of the present invention will be more apparent from the following description.